The most common pump on the market at present often comprises a pump casing, a pump body and an impeller for which a circular-arc front blade is employed. This kind of traditional pump is widely used in many fields for laying more emphasis on energy efficiency, however, the demand for pump lift is higher in some special fields as fire fighting and mining.
The existing patent for the invention titled A Spiral Flow Constant Pressure Pump with the Application No. 200710098031.5 has provided a spiral flow constant pressure pump, comprising a pump casing and an impeller; the inner wall of the pump casing is circular-arc; the impeller comprises a rear cover plate possessing a wheel hub portion, multiple front blades integrated with the rear cover plate and located in the front side thereof, and multiple auxiliary blades integrated with the rear cover plate and located in the rear side thereof; each front blade bends towards anti-clockwise direction near the circular edge of the rear cover plate and slopes towards clockwise direction, forming a bent inclined portion with a certain angle with the front surface of the rear cover plate; the auxiliary blade straightly extends to the external edge of the impeller; when the pump rotates, the outlet centrifugal force of the rear root of the bent inclined portion is greater than that of the front free edge of the bent inclined portion; the flow stream pressure of the rear root is accordingly higher than that of the front free edge; the liquid flows from the rear root to the front free edge, generating longitudinal flow; the rotated flow is generated to form spiral flow as the impeller rotates and then enters the space between the multiple front blades on the impeller for exerting pressure again, the effect of which equals to that of multiple-stage centrifugal pump, thus generating high lift and constant pressure.
However, when the above mentioned spiral flow constant pressure pump runs, the fluid in the seal cavity is not engaged in fluid exchange with the pump body operation chamber; the heat generated by mechanical seal friction cannot be taken away and the temperature of the fluid in the seal cavity will rise for continuous working, bringing hidden danger to the safety during sealed operation. In addition, the seal cavity has no air exhausting device, therefore, when the pump starts to infuse water, the air in the upper part of the seal cavity cannot be exhausted; the air and liquid are actually mixed in the seal cavity when the pump runs and cannot be exhausted, which may damage the mechanical seal.